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Visuomotor adaptation needs a validation of prediction error by feedback error.

Gaveau V, Prablanc C, Laurent D, Rossetti Y, Priot AE - Front Hum Neurosci (2014)

Bottom Line: As far as subjects remained unaware of the optical deviation and self-assigned pointing errors, prediction error alone was insufficient to induce adaptation.These results indicate a critical role of hand-to-target feedback error signals in visuomotor adaptation; consistent with recent neurophysiological findings, they suggest that a combination of feedback and prediction error signals is necessary for eliciting aftereffects.They also suggest that feedback error updates the prediction of reafferences when a visual perturbation is introduced gradually and cognitive factors are eliminated or strongly attenuated.

View Article: PubMed Central - PubMed

Affiliation: INSERM U1028, CNRS UMR5292, Lyon Neuroscience Research Center Bron, France.

ABSTRACT
The processes underlying short-term plasticity induced by visuomotor adaptation to a shifted visual field are still debated. Two main sources of error can induce motor adaptation: reaching feedback errors, which correspond to visually perceived discrepancies between hand and target positions, and errors between predicted and actual visual reafferences of the moving hand. These two sources of error are closely intertwined and difficult to disentangle, as both the target and the reaching limb are simultaneously visible. Accordingly, the goal of the present study was to clarify the relative contributions of these two types of errors during a pointing task under prism-displaced vision. In "terminal feedback error" condition, viewing of their hand by subjects was allowed only at movement end, simultaneously with viewing of the target. In "movement prediction error" condition, viewing of the hand was limited to movement duration, in the absence of any visual target, and error signals arose solely from comparisons between predicted and actual reafferences of the hand. In order to prevent intentional corrections of errors, a subthreshold, progressive stepwise increase in prism deviation was used, so that subjects remained unaware of the visual deviation applied in both conditions. An adaptive aftereffect was observed in the "terminal feedback error" condition only. As far as subjects remained unaware of the optical deviation and self-assigned pointing errors, prediction error alone was insufficient to induce adaptation. These results indicate a critical role of hand-to-target feedback error signals in visuomotor adaptation; consistent with recent neurophysiological findings, they suggest that a combination of feedback and prediction error signals is necessary for eliciting aftereffects. They also suggest that feedback error updates the prediction of reafferences when a visual perturbation is introduced gradually and cognitive factors are eliminated or strongly attenuated.

No MeSH data available.


Related in: MedlinePlus

(A) Experimental setup (modified from Prablanc et al., 1979). Targets are seen through a half-reflecting mirror (hm) and appear to be placed on the pointing surface. The target (t), mirror image of the light-emitting diodes on the upper stimulation plane is shown as a filled red circle. The prism-displaced image of the target (vt) is shown as an open red circle. The pointing hand is only visible when the volume between the mirror and the pointing surface is lit. An infrared-emitting diode is attached to the right index fingertip, the position of which is recorded. A set of either neutral or right deviating Fresnel prisms is placed in front of the eyes, uncovering a large visual field (around ± 30°). Prisms are mounted on a motorized disk (mp), which allows quick switching, from zero to any prism deviation. Vision of the target and limb was monitored, and this information was used to open or close the external feedback loop (vision of subject’s hand), and to adjust the binocular prism settings through fast step-motors. Opening or closing the feedback loop was determined by the crossing of a velocity threshold. Red solid line: physical target; red dotted line: seen target; blue solid line: physical hand; blue dashed line: seen hand; green solid line: hand velocity. (B) Layout of the targets. The four targets (T1, T2, T3, T4) used in the pre- and post-tests were located along a fronto-parallel line, at, respectively, 0, 100, 200, 300 mm right of the midline. The four targets are used during pre- and post-tests, while T3 is used during “terminal feedback error” condition exposure and no target is used during “movement prediction error” condition exposure. (C) Prism-induced visual displacement during exposure. The rightward prism deviation of a single target T3 was incrementally shifted from 4 to 25 diopters (resulting in a 142-mm rightward displacement), every block of 10 trials. (D) Real-time control of target LEDs and vision of the limb during the exposure period. Please see text for details. Solid red line: physical target; dotted red line: seen target; solid blue line: hand; vertical dashed and dotted blue line: movement onset and offset.
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Figure 1: (A) Experimental setup (modified from Prablanc et al., 1979). Targets are seen through a half-reflecting mirror (hm) and appear to be placed on the pointing surface. The target (t), mirror image of the light-emitting diodes on the upper stimulation plane is shown as a filled red circle. The prism-displaced image of the target (vt) is shown as an open red circle. The pointing hand is only visible when the volume between the mirror and the pointing surface is lit. An infrared-emitting diode is attached to the right index fingertip, the position of which is recorded. A set of either neutral or right deviating Fresnel prisms is placed in front of the eyes, uncovering a large visual field (around ± 30°). Prisms are mounted on a motorized disk (mp), which allows quick switching, from zero to any prism deviation. Vision of the target and limb was monitored, and this information was used to open or close the external feedback loop (vision of subject’s hand), and to adjust the binocular prism settings through fast step-motors. Opening or closing the feedback loop was determined by the crossing of a velocity threshold. Red solid line: physical target; red dotted line: seen target; blue solid line: physical hand; blue dashed line: seen hand; green solid line: hand velocity. (B) Layout of the targets. The four targets (T1, T2, T3, T4) used in the pre- and post-tests were located along a fronto-parallel line, at, respectively, 0, 100, 200, 300 mm right of the midline. The four targets are used during pre- and post-tests, while T3 is used during “terminal feedback error” condition exposure and no target is used during “movement prediction error” condition exposure. (C) Prism-induced visual displacement during exposure. The rightward prism deviation of a single target T3 was incrementally shifted from 4 to 25 diopters (resulting in a 142-mm rightward displacement), every block of 10 trials. (D) Real-time control of target LEDs and vision of the limb during the exposure period. Please see text for details. Solid red line: physical target; dotted red line: seen target; solid blue line: hand; vertical dashed and dotted blue line: movement onset and offset.

Mentions: The visual stimulation consisted in red light-emitting diodes (LED) placed on a plane located horizontally above the subject’s head (Figure 1A). As subjects observed the targets through a half-reflecting mirror, the targets appeared on a horizontal table on which the subjects were pointing. Because the target was a virtual image, finger-to-target masking could not influence the results. The (virtual) images of T1, T2, T3, and T4 targets were located 0 to 30 cm rightward from the subject’s sagittal axis in 10-cm increments, respectively, along a fronto-parallel line 57-cm away from the subject’s eyes (Figure 1B).


Visuomotor adaptation needs a validation of prediction error by feedback error.

Gaveau V, Prablanc C, Laurent D, Rossetti Y, Priot AE - Front Hum Neurosci (2014)

(A) Experimental setup (modified from Prablanc et al., 1979). Targets are seen through a half-reflecting mirror (hm) and appear to be placed on the pointing surface. The target (t), mirror image of the light-emitting diodes on the upper stimulation plane is shown as a filled red circle. The prism-displaced image of the target (vt) is shown as an open red circle. The pointing hand is only visible when the volume between the mirror and the pointing surface is lit. An infrared-emitting diode is attached to the right index fingertip, the position of which is recorded. A set of either neutral or right deviating Fresnel prisms is placed in front of the eyes, uncovering a large visual field (around ± 30°). Prisms are mounted on a motorized disk (mp), which allows quick switching, from zero to any prism deviation. Vision of the target and limb was monitored, and this information was used to open or close the external feedback loop (vision of subject’s hand), and to adjust the binocular prism settings through fast step-motors. Opening or closing the feedback loop was determined by the crossing of a velocity threshold. Red solid line: physical target; red dotted line: seen target; blue solid line: physical hand; blue dashed line: seen hand; green solid line: hand velocity. (B) Layout of the targets. The four targets (T1, T2, T3, T4) used in the pre- and post-tests were located along a fronto-parallel line, at, respectively, 0, 100, 200, 300 mm right of the midline. The four targets are used during pre- and post-tests, while T3 is used during “terminal feedback error” condition exposure and no target is used during “movement prediction error” condition exposure. (C) Prism-induced visual displacement during exposure. The rightward prism deviation of a single target T3 was incrementally shifted from 4 to 25 diopters (resulting in a 142-mm rightward displacement), every block of 10 trials. (D) Real-time control of target LEDs and vision of the limb during the exposure period. Please see text for details. Solid red line: physical target; dotted red line: seen target; solid blue line: hand; vertical dashed and dotted blue line: movement onset and offset.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
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Figure 1: (A) Experimental setup (modified from Prablanc et al., 1979). Targets are seen through a half-reflecting mirror (hm) and appear to be placed on the pointing surface. The target (t), mirror image of the light-emitting diodes on the upper stimulation plane is shown as a filled red circle. The prism-displaced image of the target (vt) is shown as an open red circle. The pointing hand is only visible when the volume between the mirror and the pointing surface is lit. An infrared-emitting diode is attached to the right index fingertip, the position of which is recorded. A set of either neutral or right deviating Fresnel prisms is placed in front of the eyes, uncovering a large visual field (around ± 30°). Prisms are mounted on a motorized disk (mp), which allows quick switching, from zero to any prism deviation. Vision of the target and limb was monitored, and this information was used to open or close the external feedback loop (vision of subject’s hand), and to adjust the binocular prism settings through fast step-motors. Opening or closing the feedback loop was determined by the crossing of a velocity threshold. Red solid line: physical target; red dotted line: seen target; blue solid line: physical hand; blue dashed line: seen hand; green solid line: hand velocity. (B) Layout of the targets. The four targets (T1, T2, T3, T4) used in the pre- and post-tests were located along a fronto-parallel line, at, respectively, 0, 100, 200, 300 mm right of the midline. The four targets are used during pre- and post-tests, while T3 is used during “terminal feedback error” condition exposure and no target is used during “movement prediction error” condition exposure. (C) Prism-induced visual displacement during exposure. The rightward prism deviation of a single target T3 was incrementally shifted from 4 to 25 diopters (resulting in a 142-mm rightward displacement), every block of 10 trials. (D) Real-time control of target LEDs and vision of the limb during the exposure period. Please see text for details. Solid red line: physical target; dotted red line: seen target; solid blue line: hand; vertical dashed and dotted blue line: movement onset and offset.
Mentions: The visual stimulation consisted in red light-emitting diodes (LED) placed on a plane located horizontally above the subject’s head (Figure 1A). As subjects observed the targets through a half-reflecting mirror, the targets appeared on a horizontal table on which the subjects were pointing. Because the target was a virtual image, finger-to-target masking could not influence the results. The (virtual) images of T1, T2, T3, and T4 targets were located 0 to 30 cm rightward from the subject’s sagittal axis in 10-cm increments, respectively, along a fronto-parallel line 57-cm away from the subject’s eyes (Figure 1B).

Bottom Line: As far as subjects remained unaware of the optical deviation and self-assigned pointing errors, prediction error alone was insufficient to induce adaptation.These results indicate a critical role of hand-to-target feedback error signals in visuomotor adaptation; consistent with recent neurophysiological findings, they suggest that a combination of feedback and prediction error signals is necessary for eliciting aftereffects.They also suggest that feedback error updates the prediction of reafferences when a visual perturbation is introduced gradually and cognitive factors are eliminated or strongly attenuated.

View Article: PubMed Central - PubMed

Affiliation: INSERM U1028, CNRS UMR5292, Lyon Neuroscience Research Center Bron, France.

ABSTRACT
The processes underlying short-term plasticity induced by visuomotor adaptation to a shifted visual field are still debated. Two main sources of error can induce motor adaptation: reaching feedback errors, which correspond to visually perceived discrepancies between hand and target positions, and errors between predicted and actual visual reafferences of the moving hand. These two sources of error are closely intertwined and difficult to disentangle, as both the target and the reaching limb are simultaneously visible. Accordingly, the goal of the present study was to clarify the relative contributions of these two types of errors during a pointing task under prism-displaced vision. In "terminal feedback error" condition, viewing of their hand by subjects was allowed only at movement end, simultaneously with viewing of the target. In "movement prediction error" condition, viewing of the hand was limited to movement duration, in the absence of any visual target, and error signals arose solely from comparisons between predicted and actual reafferences of the hand. In order to prevent intentional corrections of errors, a subthreshold, progressive stepwise increase in prism deviation was used, so that subjects remained unaware of the visual deviation applied in both conditions. An adaptive aftereffect was observed in the "terminal feedback error" condition only. As far as subjects remained unaware of the optical deviation and self-assigned pointing errors, prediction error alone was insufficient to induce adaptation. These results indicate a critical role of hand-to-target feedback error signals in visuomotor adaptation; consistent with recent neurophysiological findings, they suggest that a combination of feedback and prediction error signals is necessary for eliciting aftereffects. They also suggest that feedback error updates the prediction of reafferences when a visual perturbation is introduced gradually and cognitive factors are eliminated or strongly attenuated.

No MeSH data available.


Related in: MedlinePlus